Detection of bacteria and yeast species by the BACTEC 9120 automated system with the routine use of aerobic, anaerobic, and fungal media

Abstract

During the period 2006-2007 all blood cultures required by four Units at high infective risk and most of those required by other Units of the University Hospital of Palermo, Italy were performed using a BACTEC 9120 automated blood culture system with a whole set of Plus Aerobic/F, Plus Anaerobic/F, and Mycosis IC/F bottles. The aim of the study was to enable the Authors to gain firsthand experience of the cultural potentialities of the three different media, to obtain information regarding the overall and specific recovery of bacteria and yeasts from blood cultures in the hospital, and to reach a decision as to whether and when to utilize anaerobic and fungal bottles. Although very few bloodstream infections (1.8%) were associated with obligate anaerobes, the traditional routine use of anaerobic bottles was confirmed because of their usefulness in the detection not only of anaerobes, but also of gram-positive cocci and fermentative gram-negative bacilli. In this study Mycosis IC/F bottles detected 77.4% of all yeast isolates, 87.0% of yeasts belonging to Candida albicans species, and 45% of nonfermentative gram-negative bacilli resistant to chloramphenicol and tobramycin. In order to improve the diagnosis of fungaemia in high-risk patients, the routine use of Mycosis IC/F bottles was suggested when, as in the Intensive Cure Unit and in the Haematology Unit of the University Hospital of Palermo, high percentages of bloodstream infections are associated with yeasts, and/or antibiotic resistant bacteria, and/or multiple bacterial isolates, capable of inhibiting yeast growth in Plus Aerobic/F bottles.